What baseline laboratory tests should be obtained before initiating Wegovy (semaglutide) for weight management?

Baseline Laboratory Testing Before Initiating Wegovy (Semaglutide 2.4 mg)

No specific baseline laboratory tests are mandated by FDA labeling or major clinical guidelines before starting Wegovy, but targeted screening for contraindications and baseline metabolic parameters is recommended to ensure safe initiation and appropriate monitoring.

Mandatory Screening (Contraindication Assessment)

Screen for absolute contraindications before prescribing Wegovy:

• Personal or family history of medullary thyroid carcinoma (MTC) – this is an absolute contraindication based on animal studies showing thyroid C-cell tumors 1, 2
• Multiple endocrine neoplasia syndrome type 2 (MEN 2) – absolute contraindication 1, 2
• Pregnancy status – Wegovy is contraindicated in pregnancy; confirm non-pregnant status in women of childbearing potential 1, 2

Recommended Baseline Laboratory Tests

While not strictly required, the following baseline labs optimize safety monitoring and treatment decisions:

Metabolic Panel

• Comprehensive metabolic panel (CMP) including:
  • Serum creatinine and estimated glomerular filtration rate (eGFR) – to establish baseline renal function, though no dose adjustment is needed at any eGFR level 1
  • Liver enzymes (ALT, AST) – to document baseline hepatic function 1
  • Electrolytes – to assess baseline status before potential GI-related losses 1

Lipid Panel

• Fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) – to assess baseline cardiovascular risk and monitor improvement with weight loss 1
• This is particularly important because semaglutide improves lipid profiles, and documenting baseline allows tracking of cardiometabolic benefits 1

Glycemic Assessment

• Hemoglobin A1c (HbA1c) – to identify undiagnosed prediabetes or type 2 diabetes 1
• Fasting glucose – alternative or adjunct to HbA1c for glycemic assessment 1
• These tests help identify patients who may benefit from dual diabetes and weight management 1

Thyroid Function (Selective)

• Thyroid-stimulating hormone (TSH) – consider in patients with symptoms of thyroid dysfunction or risk factors 1
• GLP-1 receptors are expressed in thyroid tissue, though routine thyroid monitoring is not mandated 1

Clinical Assessment Parameters

Beyond laboratory tests, document these baseline parameters:

• Body weight and BMI – to track treatment response (target ≥5% weight loss at 3 months) 1
• Blood pressure – semaglutide reduces blood pressure, necessitating potential antihypertensive adjustment 1
• History of pancreatitis – use with caution if present, though causality not definitively established 1, 2
• History of gallbladder disease – semaglutide increases risk of cholelithiasis and cholecystitis by 38% versus placebo 2
• Gastroparesis or severe GI motility disorders – relative contraindication due to delayed gastric emptying 1, 2

Concomitant Medication Review

If patient is on diabetes medications, plan dose adjustments:

• Reduce basal insulin by 20% when starting semaglutide to prevent hypoglycemia 1
• Discontinue or reduce sulfonylureas by 50% before initiation 1
• Stop DPP-4 inhibitors entirely (no additional benefit with concurrent use) 1

Monitoring Schedule After Initiation

• Week 4 – assess GI tolerance and consider dose escalation 1
• Weeks 12-16 – re-assess weight, blood pressure, and metabolic parameters 1
• Every 3 months thereafter – monitor weight, blood pressure, cardiovascular risk factors until targets met 1
• Discontinue if <5% weight loss after 3 months at therapeutic dose 1

Common Pitfalls to Avoid

• Do not delay treatment waiting for extensive lab work; the primary screening is for contraindications (MTC/MEN 2 history, pregnancy) 1, 2
• Do not skip renal function assessment even though no dose adjustment is needed – baseline eGFR helps monitor for acute kidney injury from GI-related dehydration 1, 2
• Do not forget to assess for symptomatic gallstones – active gallbladder disease is a relative contraindication given the 38% increased risk 2
• Do not initiate at maximum dose – slow titration starting at 0.25 mg weekly minimizes GI adverse events 1, 2

Special Population Considerations

• Chronic kidney disease – no dose adjustment required at any eGFR level, but monitor closely for dehydration from GI effects 1
• Cardiovascular disease – semaglutide 2.4 mg reduces MACE by 20% in patients with established CVD, making it the preferred choice 1
• Type 2 diabetes – offers dual benefits of glycemic control and weight loss 1